1. for snorkeling, just grab a cab south to Chanakaab or beyond. Chanakaab was $10/person (thru the cab driver - he may have overcharged us...).
2. Didn't see any horse & carriage in Key West - just the Conch Train.
3. In Key West, you dock right in town. In Cozumel, you either dock at the new town pier (right in town) if your ship arrives early, or if it arrives later you're about 3 miles down the beach. Plenty of cabs, and only 5 bucks for a cab's worth of us to reach town.
4. Must sees: In Cozumel, the realtime artists in the square hidden behind Hard Rock Cafe. Carlos & Charlies (see the drunk gringos <g>). Los Cinco Soles, best shopping in Cozumel. In Key West, the Mel Fisher museum, holding many artifacts from the Atocha and other shipwrecks.